The discussion of the background of the invention herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known or part of the common general knowledge at the priority date of any of the claims.
Usually, a person needing to wear spectacles and having thus a prescription filled by an ophthalmologist goes to the premise of an optician for choosing the frame of the future spectacles. The future wearer of the spectacles may try several spectacle frames and finally chooses one of the tried frames. The optician orders a pair of lenses corresponding to the prescription. The lenses sent to the optician have been designed and manufactured according to optical criteria.
Depending on the service provided by the lens manufacturer, the optician may have to cut the lenses to the fit the spectacle frame the person has chosen or in case of “remote edging” service the optician receives the lenses already cut and only has to fit them in the spectacle frame.
The inner circumference of the openings of the chosen spectacle frame (e.g. the openings of the frame where ophthalmic lenses are intended to be mounted) can be measured very precisely by a measuring device, for example a mechanical sensor. More particularly, the openings of the frame include an inner groove and the characteristics of the groove (tilt angle with the openings, depth of the groove, etc.) can be measured by the mechanical sensor in a measuring room.
The measurements performed by the mechanical sensor on the chosen spectacle frame make it possible to order ophthalmic lenses which fit the chosen spectacle frame, on the one hand, and the wearer prescription, on the other hand.
According to the measurements performed by the mechanical sensor in the measuring room, the optician or the provider of ophthalmic lenses are able to: determine the best front surface of the lenses for the wearer according to optical criteria, for example the wearer prescription; edge and bevel the lenses to fit with the measurements performed on the chosen spectacle frame.
In the sense of the invention a step of cutting the lenses according to a spectacle frame shape is called “edging” and a step of forming a bevel on an external edged of the lens is called “beveling.”
The lenses provider has to ensure that the provided lenses are adapted to the wearer prescription and to the chosen spectacle frame.
For example, the lenses provider has to ensure that the future lenses can effectively fit the chosen frame which may have particular openings and groove.
It will be thus understood that the measurements performed on the inner circumference openings of the chosen frame and the choice of the semi-finished lens are of great importance for the provider.
The mechanical sensor provides data in the form of a list of measured points. Matching a complex surface with a list of measured points may lead be complex or inaccurate.